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Mathematics > Combinatorics

Title:A short proof of the Deutsch-Sagan congruence for connected non crossing graphs

Abstract: We give a short proof, using Lagrange inversion, of a congruence modulo 3 for
the number of connected noncrossing graphs on n vertices that was conjectured
by Emeric Deutsch and Bruce Sagan. A more complicated proof had been given
earlier by S.-P. Eu, S.-C. Liu, and Y.-N. Yeh.